Single-digit temperatures early Thursday, the coldest day in almost a year, sparked a slew of transportation delays around the region, leaving ­riders disgruntled at late arrivals and missed appointments.

As bitter cold swept across Eastern Massachusetts during the morning commute, 10 of the MBTA system’s 129 trains experienced mechanical problems, while a broken rail at the Central Square T stop, also caused by extreme cold, interrupted service for almost two hours.

Officials said that the effects of the cold — Boston dropped to 7 degrees just before 6 a.m — could have been much worse and that many of Thursday’s problems were caused by an aging, under­funded train system.

Thursday’s delays were a marked improvement over a similarly cold day two years ago, when the temperature reached a bone-chilling 2 ­degrees below zero, sparking ­delays in 63 percent of the morning commuter rail trains and causing 23 rapid-transit trains and trolleys on the ­MBTA to stall on the tracks.

After forecasts predicted stinging temperatures, Scott said Thursday evening that she had anticipated a challenging day and had put staff on guard to quickly respond to potential problems.

Train systems, she said, “can take snow up to 3, 4, or even 5 inches without huge problems, but whenever you get extremely cold conditions,” Scott said, “those are the conditions that are always absolutely an ­extreme challenge.”

Because of the broken rail line, passengers were herded to shuttle buses to take them ­between Harvard Square and Kendall Square, a process that some passengers called chaotic, even with automated announce­ments. Other trains stalled after their air hoses froze, impeding their propulsion systems.

Some of the cold weather problems, Scott said, are exacerbated by the aging T system. But, she said, no system would be immune to these types of ­occurrences.

“Even if you had completely new equipment, you could wind up having these issues,” she said.

Scott said that while she was proud of the performance of MBTA staff on Thursday and their efforts to keep trains running, she recognized that the T must still do better.

“I can appreciate the fact that there were literally folks left out in the cold today,” she said.

Days as cold as Thursday come infrequently in Boston. In 2012, there was only one day when the weather reached single digits: Jan. 15, when the temperature plunged to 6 ­degrees, according to the ­National Weather Service. The year before, there were two days in the single digits: Jan. 23, when the low was 5 ­degrees, and Jan. 24, when the temperature reached 2 below zero.

Further inland, temperatures Thursday dropped considerably lower than in Boston: Orange reached 10 below zero, according to the National Weather Service meteorologist Charlie Foley. Milton’s Blue Hill Meteorological Observatory recorded its coldest temperatures in two years, registering 2 ­degrees Thursday.

But the arctic freeze will not be around for long: Temperatures in Boston next week will probably rise to the 40s or even the low 50s, Foley said.

On the region’s commuter rail lines, the mechanical issues caused by Thursday’s frigid temperatures were wide-ranging: a broken rail, a frozen valve, malfunctioning signal systems (many of which date from the 1950s or 1960s), disabled freight and Amtrak trains. But most of those problems were outside the authority of the Massachusetts Bay Commuter Railroad Company, spokesman Scott Farmelant said.

Ten trains on the Lowell line and three trains on the Haverhill line were delayed for 3 to 38 minutes because of a signal failure on a portion of the line that is maintained by another company, Pan Am Railways, he said.

Two disabled Amtrak trains also prevented commuter rail trains traveling from ­Providence, Franklin, Middleborough, Stoughton, and ­Needham from entering South Station, and delays ranged from 7 to 34 minutes. One ­MBTA train had to push an Amtrak train into the station.

“There is only one way to prevent cold-weather delays: increased capital investment into the infrastructure, in particular signals, switches, and bridges,” Farmelant said.

“With a system that spans halfway across the state on two lines and from Cape Ann to Kingston, R.I., weather is far more likely to take its toll,” he said. “The best way to respond is by continually upgrading the system with new signals and signal lines.”

Broken rails, like the one that blocked the Red Line ­MBTA train early Thursday after­noon, are a common problem on train systems around the country, said Martin Schroeder, chief engineer at the American Public Transportation Association. It is simple physics, he said: As the temperature nosedives, the rails can contract, causing them to snap off their bearings.

Some train delays, he said, could also occur as train operators slow down in the cold to watch out for broken rails and lessen the impact if they do hit a broken one.

Some of the cold weather problems, he said, can be prevented with cutting-edge technology that help eliminate condensation, which affects brake systems. But it is a constant battle for most any transportation system. “When you get delays in passenger train systems, it’s for a good reason, because they want to be as safe as possible,” Schroeder said.

Wintry weather poses a challenge for other transit systems, including the Chicago Transit Authority, where cold weather occasionally causes problems with electrical switches or rail car doors, spokeswoman Catherine Hosinski said. But because the Chicago Transit Authority staff conducts inspections before bouts of cold weather, they usually experience few problems in single-digit temperatures.

For Boston-area commuters like Erica Mattison, 31, of Dorchester, who takes the Red Line from Ashmont Station to Downtown Crossing almost daily, crowded platforms and trains caused by the weather delays meant arriving to work late and grumpy Thursday.

“It took something like 40 minutes, when normal travel time is about 20 minutes,” said Mattison. “It makes for a frustrated bunch of people.”

Mattison said the delays began at the Ashmont Station, where riders had packed onto the platform, and compounded at each stop.

“It was very crowded and basically standing room only, more so than usual because you had a pileup of people,” she said. “It was difficult for people getting off at later stops, because the train was too packed. It was all pretty chaotic.”

Globe correspondents Lauren Dezenski and Colin A. Young contributed to this report. ­Martine Powers can be reached at mpowers@globe.com.